Statistical inference for seed mortality and germination with seed bank experiments

Siegmund, Gregor-Fausto; Geber, Monica A.

doi:10.1002/ecy.3948

“…2B). The model we fit to the observational data jointly accounts for loss of seeds from the seed bank through mortality and germination (Siegmund and Geber 2022). Germination occurs once a year in the winter, and is estimated from the seeds that germinate each year.…”

Section: Methodsmentioning

confidence: 99%

Bet hedging is not sufficient to explain germination patterns of a winter annual plant

Siegmund

¹

,

Moeller

²

,

Eckhart

³

et al. 2022

Preprint

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Bet hedging consists of life history strategies that buffer against environmental variability by trading off immediate and long-term fitness. Delayed germination in annual plants is a classic example of bet hedging, and is often invoked to explain low germination fractions. We examined whether bet hedging explains low and variable germination fractions among 20 populations of the winter annual plant Clarkia xantiana ssp. xantiana that experience substantial variation in reproductive success among years. Leveraging 15 years of demographic monitoring and 3 years of field germination experiments, we assessed the fitness consequences of seed banks and compared optimal germination fractions from a density-independent bet-hedging model to observed germination fractions. We did not find consistent evidence of bet hedging or the expected trade-off between arithmetic and geometric mean fitness, though delayed germination increased long-term fitness in 7 of 20 populations. Optimal germination fractions were 2 to 5 times higher than observed germination fractions, and among-population variation in germination fractions were not correlated with risks across the life cycle. Our comprehensive test suggests that bet hedging is insufficient to explain the observed germination patterns. Understanding variation in germination strategies will likely require integrating bet hedging with complementary forces shaping the evolution of delayed germination.

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